Measuring apparatus for measuring flow rate of a fluid

Abstract

A metal plate is supported by a base, and is disposed inside a main passage so as to be generally parallel to a direction of flow of a fluid being measured through the main passage, and a circuit board and a flow rate detecting element are disposed so as to be positioned generally in a common plane with a front surface of the metal plate. A circuit housing portion formed integrally on the base is disposed on the front surface of the metal plate so as to surround the circuit board, an electrical connection portion between the circuit board and the flow rate detecting element, and an electrical connection portion between the circuit board and a connector portion. A measuring passage groove forming portion formed integrally on the base is disposed on the front surface of the metal plate, and functions together with the metal plate to constitute a measuring passage. In addition, the circuit housing portion is charged with a sealing gel, and a cover is mounted so as to cover the circuit housing portion.

1. A flow rate measuring apparatus comprising:
 a measuring passage through which passes a portion of a fluid being measured flowing through a main passage; 
 a flow rate detecting element in which a sensor portion is formed on a front surface of a flat substrate, said flow rate detecting element being disposed such that said sensor portion is exposed inside said measuring passage; 
 a circuit board on which a control circuit is mounted for driving said sensor portion and processing a signal therefrom; 
 a connector portion for sending and receiving signals between said circuit board and an external portion; 
 a resin base, said connector portion being formed integrally on said base, said connector portion being positioned outside said main passage and said base projecting inside said main passage; and 
 a metal plate supported by said base, said metal plate being disposed inside said main passage so as to be substantially parallel to a direction of flow of said fluid being measured through said main passage, 
 wherein: 
 said circuit board is disposed on said metal plate so as to be positioned substantially in a common plane with a front surface of said metal plate, 
 said flow rate detecting element is positioned substantially in a common plane with said front surface of said metal plate and disposed on said metal plate in close proximity to an opposite end of said circuit board from said connector portion, 
 a circuit housing portion is disposed on said front surface of said metal plate so as to surround said circuit board, an electrical connection portion between said circuit board and said flow rate detecting element, and an electrical connection portion between said circuit board and said connector portion, 
 a cover is mounted so as to cover said circuit housing portion, 
 a measuring passage groove forming portion is disposed on a front surface of said metal plate at an opposite end of said circuit housing portion from said connector portion and functions together with said metal plate to constitute said measuring passage, and 
 said circuit housing portion and said measuring passage groove forming portion are formed integrally on said base. 
 
   
   
     2. The flow rate measuring apparatus according to  claim 1 , further comprising:
 an intake air temperature sensor for measuring a temperature of said fluid being measured, wherein the intake air temperature sensor has leads that are electrically connected directly to said circuit board and is disposed so as to be exposed to said fluid being measured outside said measuring passage, said leads being fixed and sealed between said circuit housing portion and said cover. 
 
   
   
     3. The flow rate measuring apparatus according to  claim 2 , wherein:
 said intake air temperature sensor is disposed so as to be contained inside an outline of a main body portion constituted by a projecting portion of said base inside said main passage, said metal plate, and said cover when viewed from a direction of flow of said fluid being measured, and inside an outline of said main body portion when viewed from a direction of projection inside said main passage. 
 
   
   
     4. The flow rate measuring apparatus according to  claim 3 , wherein:
 said intake air temperature sensor is disposed inside an intake air temperature sensor installation portion formed on said main body portion, said intake air temperature sensor installation portion being open from a first side in a direction perpendicular to said direction of projection of said main body portion inside said main passage and perpendicular to said direction of flow said fluid being measured, through an upstream side in said direction of flow of said fluid being measured, to a second side in said direction perpendicular to said direction of projection of said main body portion inside said main passage and perpendicular to said direction of flow of said fluid being measured. 
 
   
   
     5. The flow rate measuring apparatus according to  claim 3 , wherein said measuring passage comprises:
 an inflow aperture formed in a first of two wall surfaces constituted by short sides of a cross section of the main body portion; and 
 an outflow aperture formed on a leading end surface of the main body portion in the direction of projection. 
 
   
   
     6. The flow rate measuring apparatus according to  claim 1 , wherein:
 a first peripheral wall member is formed integrally with said circuit housing portion so as to function together with said circuit housing portion to surround said electrical connection portion between said circuit board and said flow rate detecting element, 
 a second peripheral wall member is formed integrally with said circuit housing portion so as to function together with said circuit housing portion to surround said electrical connection portion between said circuit board and said connector portion, and 
 a sealing gel is charged inside a space bounded by said first peripheral wall member and said circuit housing portion and inside a space bounded by said second peripheral wall member and said circuit housing portion. 
 
   
   
     7. A flow rate measuring apparatus comprising:
 a measuring passage through which passes a portion of a fluid being measured flowing through a main passage; 
 a flow rate detecting element in which a sensor portion is foamed on a front surface of a flat substrate, said flow rate detecting element being disposed such that said sensor portion is exposed inside said measuring passage; 
 a circuit board on which a control circuit is mounted for driving said sensor portion and processing a signal therefrom; and 
 a connector portion for sending and receiving signals between said circuit board and an external portion; 
 a resin base, said connector portion being formed integrally on said base, said connector portion being positioned outside said main passage and said base projecting inside said main passage; and 
 a metal plate supported by said base, said metal plate being disposed inside said main passage so as to be substantially parallel to a direction of flow of said fluid being measured inside said main passage, 
 wherein: 
 said circuit board is disposed on said metal plate so as to be positioned substantially in a common plane with a front surface of said metal plate, 
 said flow rate detecting element is positioned substantially in a common plane with said front surface of said metal plate and disposed on said metal plate in close proximity to an opposite end of said circuit board from said connector portion, 
 a circuit housing portion is disposed on said front surface of said metal plate so as to surround said circuit board, an electrical connection portion between said circuit board and said flow rate detecting element, and an electrical connection portion between said circuit board and said connector portion, 
 a resin cover is mounted so as to cover said circuit housing portion, 
 a measuring passage groove forming portion is disposed on a front surface of said metal plate at an opposite end of said circuit housing portion from said connector portion and functions together with said metal plate to constitute said measuring passage, 
 said circuit housing portion is formed integrally on said base, and 
 said measuring passage groove forming portion is formed integrally on said cover. 
 
   
   
     8. The flow rate measuring apparatus according to  claim 7 , wherein: said metal plate is insert-molded integrally together with said base. 
   
   
     9. The flow rate measuring apparatus according to  claim 7 , further comprising:
 an intake air temperature sensor for measuring a temperature of said fluid being measured, wherein the intake air temperature sensor has leads that are electrically connected directly to said circuit board and is disposed so as to be exposed to said fluid being measured outside said measuring passage, said leads being fixed and sealed between said circuit housing portion and said cover. 
 
   
   
     10. The flow rate measuring apparatus according to  claim 9 , wherein:
 said intake air temperature sensor is disposed so as to be contained inside an outline of a main body portion constituted by a projecting portion of said base inside said main passage, said metal plate, and said cover when viewed from a direction of flow of said fluid being measured, and inside an outline of said main body portion when viewed from a direction of projection inside said main passage. 
 
   
   
     11. The flow rate measuring apparatus according to  claim 10 , wherein:
 said intake air temperature sensor is disposed inside an intake air temperature sensor installation portion formed on said main body portion, said intake air temperature sensor installation portion being open from a first side in a direction perpendicular to said direction of projection of said main body portion inside said main passage and perpendicular to said direction of flow said fluid being measured, through an upstream side in said direction of flow of said fluid being measured, to a second side in said direction perpendicular to said direction of projection of said main body portion inside said main passage and perpendicular to said direction of flow of said fluid being measured. 
 
   
   
     12. The flow rate measuring apparatus according to  claim 10 , wherein said measuring passage comprises:
 an inflow aperture formed in a first of two wall surfaces constituted by short sides of a cross section of the main body portion; and 
 an outflow aperture formed on a leading end surface of the main body portion in the direction of projection. 
 
   
   
     13. The flow rate measuring apparatus according to  claim 7 , wherein:
 a first peripheral wall member is formed integrally with said circuit housing portion so as to function together with said circuit housing portion to surround said electrical connection portion between said circuit board and said flow rate detecting element, 
 a second peripheral wall member is formed integrally with said circuit housing portion so as to function together with said circuit housing portion to surround said electrical connection portion between said circuit board and said connector portion, and 
 a sealing gel is charged inside a space bounded by said first peripheral wall member and said circuit housing portion and inside a space bounded by said second peripheral wall member and said circuit housing portion.